These instruments are conventionally used for the measurement of infrasonic waves also called infrasound, that is to say with very small pressure variations (typically comprised in the range from a millipascal to around a hundred pascals) of which the frequency is less than 20 Hz; these instruments measure the shape of the waves more than the intensity of the corresponding signal. These instruments are of a very different type to that of barometers, which measure the atmospheric pressure, that is to say values of the order of 105 Pa, with an accuracy of the order of about a hundred, or a thousand, pascals.
Infrasonic waves are in particular produced by events, whether or not natural, of which the following (non-exhaustive) list gives an idea of the extent of the applications: the study of volcanic eruptions, the study and monitoring of the reentry into the atmosphere of meteorites or satellites at the end of life, counting and location of avalanches, monitoring nuclear explosions, measuring gravity waves induced by the movements of convection in the atmosphere, the study of atmospheric models, studies of inaudible waves generated by wind turbines, trains, aircraft, underground trains.
On account of their very low frequency, infrasonic waves have the property of propagating over long distances in the various layers of the atmosphere while being appreciably less attenuated than waves in the audible range: several times around the earth for high-energy phenomena such as nuclear explosions, several thousand kilometers for certain natural phenomena such as volcanic eruptions.
To efficiently measure infrasonic waves, microbarometers must have the following performance:                sensitivity of the order of the mPa, i.e. 10−8 below ambient atmospheric pressure,        intrinsic noise less than the minimum noise measured at the surface of the Earth,        bandwidth enabling the useful detection bands (0.001 Hz to 10 Hz) to be covered and if possible the absolute static pressure of the location;        flat response within the bandwidth,        highest possible dynamic range of measurement to detect all the phenomena without needing to filter the low frequencies (gravity waves), or even the continuous component which is the pressure of the location, variable according to altitude.        resonance frequency which must be situated outside the detection band,        very little influence by the external temperature on the sensor, which would then be confused with low frequency waves.        
Microbarometers with a bellows have existed for approximately 50 years. They use the principle of barometric measurement to access the variations in pressure from zero to 20 Hz. The reference pressure is a primary vacuum enclosed in an anaerobic capsule of bellows form generally disposed vertically on a base. Any variation in pressure deforms that bellows while generating linear displacement in its upper part. In the existing technologies, this displacement is measured by an electromagnetic sensor of LVDT type (LVDT being an acronym for “Linear Variable Differential Transformer”), that is to say a passive electrical (inductive) sensor of linear displacements, as is described in particular in the publication “LDG microbarometers: description and performances—Network design—Gérard Ruzié—Ghislain Claque—CTBTO Informal infrasound workshop May 2 to 4, 1996 CEA Bruyères-le-Châtel France.”
Microbarometers with a bellows, associated with their electromagnetic sensors, have been optimized over several decades by the specialists of infrasonic waves who conventionally master the mechanics of accuracy and electromagnetism. This is the case with the microbarographs of MB 2000 and MB 2005 type developed by the CEA since the 1970's.
Despite the numerous optimizations, the current microbarometers with a bellows have a limited spectral band of measurement, are sensitive electromagnetic perturbations and maintain a degree of thermal sensitivity on account of the mounting.